TABLE OF CONTENTS

NAME

Mojo::IOLoop::Delay - Manage callbacks and control the flow of events

SYNOPSIS

use Mojo::IOLoop::Delay;

# Synchronize multiple events
my $delay = Mojo::IOLoop::Delay->new;
$delay->steps(sub { say 'BOOM!' });
for my $i (1 .. 10) {
  my $end = $delay->begin;
  Mojo::IOLoop->timer($i => sub {
    say 10 - $i;
    $end->();
  });
}
$delay->wait;

# Sequentialize multiple events
Mojo::IOLoop::Delay->new->steps(

  # First step (simple timer)
  sub {
    my $delay = shift;
    Mojo::IOLoop->timer(2 => $delay->begin);
    say 'Second step in 2 seconds.';
  },

  # Second step (concurrent timers)
  sub {
    my ($delay, @args) = @_;
    Mojo::IOLoop->timer(1 => $delay->begin);
    Mojo::IOLoop->timer(3 => $delay->begin);
    say 'Third step in 3 seconds.';
  },

  # Third step (the end)
  sub {
    my ($delay, @args) = @_;
    say 'And done after 5 seconds total.';
  }
)->wait;

# Handle exceptions in all steps
Mojo::IOLoop::Delay->new->steps(
  sub {
    my $delay = shift;
    die 'Intentional error';
  },
  sub {
    my ($delay, @args) = @_;
    say 'Never actually reached.';
  }
)->catch(sub {
  my ($delay, $err) = @_;
  say "Something went wrong: $err";
})->wait;

DESCRIPTION

Mojo::IOLoop::Delay manages callbacks and controls the flow of events for Mojo::IOLoop, which can help you avoid deep nested closures and memory leaks that often result from continuation-passing style.

EVENTS

Mojo::IOLoop::Delay inherits all events from Mojo::EventEmitter and can emit the following new ones.

error

$delay->on(error => sub {
  my ($delay, $err) = @_;
  ...
});

Emitted if an exception gets thrown in one of the steps, breaking the chain, fatal if unhandled.

finish

$delay->on(finish => sub {
  my ($delay, @args) = @_;
  ...
});

Emitted once the active event counter reaches zero and there are no more steps.

ATTRIBUTES

Mojo::IOLoop::Delay implements the following attributes.

ioloop

my $ioloop = $delay->ioloop;
$delay     = $delay->ioloop(Mojo::IOLoop->new);

Event loop object to control, defaults to the global Mojo::IOLoop singleton.

METHODS

Mojo::IOLoop::Delay inherits all methods from Mojo::EventEmitter and implements the following new ones.

begin

my $cb = $delay->begin;
my $cb = $delay->begin($offset);
my $cb = $delay->begin($offset, $len);

Indicate an active event by incrementing the active event counter, the returned callback needs to be called when the event has completed, to decrement the active event counter again. When all callbacks have been called and the active event counter reached zero, "steps" will continue.

# Capture all arguments except for the first one (invocant)
my $delay = Mojo::IOLoop->delay(sub {
  my ($delay, $err, $stream) = @_;
  ...
});
Mojo::IOLoop->client({port => 3000} => $delay->begin);
$delay->wait;

Arguments passed to the returned callback are spliced with the given offset and length, defaulting to an offset of 1 with no default length. The arguments are then combined in the same order "begin" was called, and passed together to the next step or "finish" event.

# Capture all arguments
my $delay = Mojo::IOLoop->delay(sub {
  my ($delay, $loop, $err, $stream) = @_;
  ...
});
Mojo::IOLoop->client({port => 3000} => $delay->begin(0));
$delay->wait;

# Capture only the second argument
my $delay = Mojo::IOLoop->delay(sub {
  my ($delay, $err) = @_;
  ...
});
Mojo::IOLoop->client({port => 3000} => $delay->begin(1, 1));
$delay->wait;

# Capture and combine arguments
my $delay = Mojo::IOLoop->delay(sub {
  my ($delay, $three_err, $three_stream, $four_err, $four_stream) = @_;
  ...
});
Mojo::IOLoop->client({port => 3000} => $delay->begin);
Mojo::IOLoop->client({port => 4000} => $delay->begin);
$delay->wait;

data

my $hash = $delay->data;
my $foo  = $delay->data('foo');
$delay   = $delay->data({foo => 'bar'});
$delay   = $delay->data(foo => 'bar');

Data shared between all "steps".

# Remove value
my $foo = delete $delay->data->{foo};

# Assign multiple values at once
$delay->data(foo => 'test', bar => 23);

pass

$delay = $delay->pass;
$delay = $delay->pass(@args);

Increment active event counter and decrement it again right away to pass values to the next step.

# Longer version
$delay->begin(0)->(@args);

remaining

my $remaining = $delay->remaining;
$delay        = $delay->remaining([]);

Remaining "steps" in chain, stored outside the object to protect from circular references.

steps

$delay = $delay->steps(sub {...}, sub {...});

Sequentialize multiple events, every time the active event counter reaches zero a callback will run, the first one automatically runs during the next reactor tick unless it is delayed by incrementing the active event counter. This chain will continue until there are no more callbacks, a callback does not increment the active event counter or an exception gets thrown in a callback.

wait

$delay->wait;

Start "ioloop" and stop it again once an "error" or "finish" event gets emitted, does nothing when "ioloop" is already running.

SEE ALSO

Mojolicious, Mojolicious::Guides, http://mojolicio.us.